1. Field of the Invention
The present invention relates to a film-bitumen combination with at least three layers that is used in particular as a membrane to cover roof areas.
2. The Prior Art
Many different backing films have been disclosed for bitumen membranes that are designed in particular to seal roof areas, but all of them have serious disadvantages. As a result of the migration of mineral oils into the plastic web as well as of thermal expansion of both the bitumen membrane and the plastic film, the plastic film detaches from the bitumen membrane in the course of time (curling). The material combinations often have very low thermo-mechanical strength properties, particularly when they are walked on. In addition, complicated processes are required to produce such material combinations.